Contractions Of Vein Research Articles

Endothelin-1 and its receptors on haemorrhoidal tissue: a potential site for therapeutic intervention.

Haemorrhoids is a common anorectal condition affecting millions worldwide. We have studied the effect of endothelin-1 (ET-1) and the role of endothelin ETA and ETB receptors in haemorrhoid tissue. Protein expression of ET-1, ETA and ETB receptors were compared between haemorrhoids and normal rectal submucosa using Western blot analysis, with the localization of proteins determined by autoradiography and immunohistochemistry. Effects of ET-1 and sarafotoxin 6a on human colonic and rectal arteries and veins was assessed by wire myography and the involvement of receptor subtypes established by selective antagonists. Dense binding of [125 I]-ET-1 to haemorrhoidal sections was reduced by selective receptor antagonists. A higher density of ETB than ETA receptors was found in haemorrhoidal, than in control rectal tissue and confirmed by Western blot analysis. ETA and ETB receptors were localized to smooth muscle of haemorrhoidal arteries and veins, with ETB receptors on the endothelium. Human colonic and rectal arteries and veins were similarly sensitive to ET-1 and affected by the ETA selective antagonist, but sarafotoxin S6a-induced contractions were more pronounced in veins and antagonized by a selective ETB receptor antagonist. ETA and ETB receptors are present in human haemorrhoids with ETB receptors predominating. ETA receptors are activated by ET-1 to mediate a contraction in arteries and veins, but the latter are selectively activated by sarafotoxin S6a - a response that involves ETB receptors at low concentrations. Selective ETB agonists may have therapeutic potential to reduce congestion of the haemorrhoidal venous sinusoids.

ZD0947, a sulphonylurea receptor modulator, detects functional sulphonylurea receptor subunits in murine vascular smooth muscle ATP-sensitive K+ channels

In order to identify functional sulphonylurea receptor (SUR.x) subunits of native ATP-sensitive K+ channels (KATP channels) in mouse portal vein, the effects of ZD0947, a SUR.x modulator, were investigated on spontaneous portal vein contractions, macroscopic membrane currents and unitary currents recorded (using patch-clamp techniques) in freshly dispersed mouse portal vein myocytes. Spontaneous contractions in mouse portal vein were reversibly reduced by ZD0947 in a concentration-dependent manner (Ki =293nM). The relaxation elicited by 3µM ZD0947 was antagonized by the additional application of glibenclamide (300nM), but not gliclazide (100–300nM). In the conventional whole-cell configuration, 100µM ZD0947 elicited inward glibenclamide-sensitive currents at a holding potential of −60mV that demonstrated selectivity for K+(i.e. KATP currents). The peak amplitude of the membrane current elicited by 30µM or 100µM ZD0947 was smaller than that elicited by 100µM pinacidil at −60mV. In the cell-attached mode, 100µM ZD0947 activated glibenclamide-sensitive K+ channels with a conductance (35 pS) similar to that of recombinant Kir6.1/SUR2B channels that were expressed in HEK293 cells and activated by 100µM ZD0947. These results demonstrate that ZD0947 caused a significant vascular relaxation through the activation of KATP channels and that SUR2B may be the major functional subunit of SUR.x in mouse portal vein KATP channels, based on its pharmacological selectivity.

Sulodexide Promotes Venous Contraction in Rat Inferior Vena Cava

Sulodexide (SDX) is a highly purified glycosaminoglycan composed of fast-moving heparin (80%) and dermatan sulfate (20%). SDX has both antithrombotic and profibrinolytic properties with reported benefits in chronic venous disease and other thrombotic and atherosclerotic vascular disorders. However, the effects of SDX on the vein wall structure and function are unclear. We have previously shown that matrix metalloproteinases 2 and 9 cause venous relaxation, and other studies have suggested that SDX may inhibit matrix metalloproteinase 9. The purpose of this study was to test whether SDX affects venous function and whether its venous effects are different from those in the arteries. Male rat inferior vena cava (IVC), abdominal aorta, and mesenteric artery were harvested and 3-mm circular segments were equilibrated under 0.5g, 2g, and 1g basal tension, respectively, in a tissue bath containing Krebs solution bubbled with 95% O2 5% CO2 at 37°C, and the changes in isometric contraction were recorded. Vessel segments were precontracted with the α-adrenergic receptor agonist phenylephrine (PHE, 3 × 10−7 M), and the changes in the vessel response to SDX (0.001-1 mg/mL) were measured. The % venous/arterial contraction or relaxation was calculated, and the data were presented as means ± standard error of the mean and analyzed with t-test, with P < .05 significant. In the IVC, aorta, and mesenteric artery, PHE (3 × 10−7 M) caused submaximal contraction that remained steady for at least 1 hour. In PHE-precontracted IVC, SDX caused concentration-dependent increases in contraction that reached a maximum at 1 mg/mL (SDX 62.8 ± 3.9 vs control 0.0; P < .01). In contrast, in PHE-precontracted aorta and mesenteric artery, SDX caused concentration-dependent relaxation compared with control (maximum 45.4 ± 6.0 vs 6.7 ± 6.6; 39.3 ± 6.2 vs 0.0, respectively; P < .05). SDX potentiates contraction in veins while causing relaxation in arteries. The mechanisms may involve differential effects of SDX on different matrix metalloproteinase subtypes, protease-activated receptors, and integrins in the veins vs arteries and need to be further examined. The results may have clinical implications as SDX may be helpful as a venotonic agent for chronic venous disease while promoting arterial dilation and decreasing arterial pressure.

Analysis of Threshold Stenosis by Multiplanar Venogram and Intravascular Ultrasound for Predicting Clinical Improvement After Iliofemoral Vein Stenting: Results From the VIDIO Study

Selection of patients for iliofemoral vein stenting requires the identification and quantification of stenotic lesions with imaging such as multiplanar venography (MPV) and intravascular ultrasound (IVUS). The Venogram Versus Intravascular Ultrasound for Diagnosing Iliofemoral Vein Obstruction (VIDIO) trial showed IVUS to be more sensitive than MPV for identifying “significant” iliofemoral vein stenosis. To date, the comparative utility of these imaging studies using the customary 50% treatment threshold for stenosis severity has not been prospectively validated against clinical improvement. The multicenter VIDIO trial prospectively enrolled 100 symptomatic patients (clinical, etiologic, anatomic, and pathophysiologic [CEAP] class 4-6) with suspected iliofemoral venous outflow disease. Venous stenting for presumed significant iliofemoral vein stenosis was performed on 68 patients. Each underwent baseline and poststenting MPV and IVUS to compare the diagnostic and clinical utility of the tests. Based on imaging, stenosis was characterized as nonthrombotic (ie, compression) in 48 patients and post-thrombotic (ie, luminal scar, sclerotic vein contraction) in 20 patients. The Revised Venous Clinical Severity Score was the clinical index for which anatomic imaging measurements were consistently related to patient outcome. A 4-point reduction in the Revised Venous Clinical Severity Score between baseline and 6 months was used as an indicator of clinical improvement for calculating sensitivities and specificities for MPV-determined percentage diameter reduction and IVUS-determined percentage diameter and area reduction. Receiver operating characteristic curve analysis was used to determine the optimal diameter and area thresholds for clinical improvement. The validity of each imaging measure was assessed with respective areas under the curve (AUCs), calculating P values estimating the probability that a measure was of greater value than chance alone. Clinical improvement after stenting was best predicted by IVUS-determined baseline stenosis, either by diameter (AUC, .64; P = .046; cutoff >55.7%) or area reduction (AUC, .64; P = .043; cutoff >53.6%). MPV-determined baseline stenosis was not predictive (AUC, .58; P = .290; cutoff >51.9%). Evaluating lumen improvement from baseline to after intervention revealed that IVUS-determined area change was the best measure (AUC, .70; P = .003; cutoff >40.5%), followed by IVUS-determined diameter change (AUC, .66; P = .020; cutoff >45.6%). MPV-determined diameter change did not predict clinical improvement (AUC, .56; P = .370; cutoff >37.5%). In the 48-patient nonthrombotic subset, IVUS diameter measurements of baseline stenosis were significantly predictive (AUC, .67; P = .029; cutoff >61.2%). MPV was not predictive (AUC, .61; P = .17; cutoff >51.9%). The measurement with the most predictive utility for clinical improvement was stenotic change in the nonthrombotic subset, with an AUC of .75 for both IVUS area and diameter measurements (P = .001). MPV-determined diameter change in the nonthrombotic subset had borderline predictive utility for symptom improvement (AUC, .66; P = .05). At the time of intervention, IVUS appears to have better predictive utility than MPV for identifying iliofemoral vein stenosis in CEAP class 4-6 patients that, when treated, results in significant symptom improvement. These findings for the entire cohort corroborate the conventional 50% threshold as defining a clinically significant stenosis that, when stented, has significant predictive value for symptom improvement. In nonthrombotic patients, however, a higher threshold of >61% diameter stenosis may better predict clinical improvement.

Moderate hypothermia attenuates α1-adrenoceptor-mediated contraction in human varicose spermatic vein: The role of nitric oxide(Short communication).

The effects of moderate hypothermia (28°C) on the response of human varicose spermatic vein to α1-adrenoceptor agonist phenylephrine and the role of endothelial nitric oxide (NO) in these effects were studied. Concentration-response curves for phenylephrine (10-9 to 3 × 10-4 M) were recorded in rings with and without endothelium at 37 and 28°C. To further analyze the role of NO, in the response to phenylephrine during hypothermia, the effects of this agonist in the presence of NG-nitro-L-arginine methyl ester (10-4 M) were also determined. Under every condition tested, phenylephrine produced a marked, concentration-dependent contraction. Sensitivity of intact veins to the agonist was consistently lower at 28°C than at 37°C. There was no significant difference in phenylephrine response at 28 and 37°C in vessels without endothelium but at 28°C veins without endothelium showed a higher sensitivity than intact veins to phenylephrine. The sensitivity of veins with and without endothelium to nitroprusside (10-9 to 3 × 10-3 M) was significantly decreased during hypothermia, and endothelium removal did not affect the relaxation to this nitrovasodilator. These results suggest that moderate hypothermia decreases the sensitivity of human varicose spermatic vein to phenylephrine probably by increasing the availability of endothelial NO.

Exposure to sub-acute doses of fipronil and buprofezin in combination or alone induces biochemical, hematological, histopathological and genotoxic damage in common carp (Cyprinus carpio L.)

Use of pesticides or insecticides can be highly toxic to aquatic life forms due to leaching and agricultural runoff, rains or flood. Fipronil (FP) is a GABA receptor inhibitor, while buprofezin (BPFN) is an insect growth regulator. Presently, we exposed groups of aquaria acclimated carp fish (Cyprinus carpio) for 96h to sub-lethal concentrations of fipronil (400μgL−1; 9.15×10−7molL−1) and buprofezin (BPFN, 100mgL−1; 1.072×10−6molL−1) singly or in combination. The extent of damage was assessed at biochemical, hematological, molecular biological and histopathological level. Results obtained in treated fish were compared statistically with those of control non-treated fish and also among treatment groups. Significance level was p<0.05. Compared to control, serum total protein and globulin concentrations decreased significantly (p<0.0001) in fish treated with FP; while albumin concentration remained unaltered with all treatments. Glucose concentration decreased significantly (p<0.002) in fish treated with FP. In contrast, combined FP+BPFN treatment and BPFN treatment caused insignificant elevation of glucose concentration. Hematological assessment demonstrated significant decrease in red blood cell and thrombocyte counts, hemoglobin concentration and hematocrit percent; while white blood cell count showed an increase in all treatment groups (p<0.0001). Blood smears from pesticide treated fish revealed aberrant erythrocyte morphologies which included necrosis, micronuclear formation and hyperchromatosis. DNA laddering assay carried out on whole blood demonstrated excessive smear formation in combined FP+BPFN and BPFN treatment groups but no smear formation was noticeable in FP treated fish. Compared to control, whole blood DNA content increased significantly in the combined FP+BPFN and BPFN treatment groups (p<0.001 and p<0.009). With all treatments histopathological changes observed in the gills were: epithelial uplifting and necrosis of lamellae, lamellar atrophy, disruption of cartilaginous core, fusion and disorganization of lamellae and telangiectasia. In liver these were: karyorrhexis, hepatocellular hypertrophy, nuclear hypertrophy, melanomacrophage aggregates and central vein contraction, while in the kidney: deterioration of glomerulus and dilatation of Bowman’s space, dilatation of renal tubules, thyroidisation, altered tubular lumen, nuclear hypertrophy, cellular atrophy, and cellular necrosis were the outcome. Our study revealed that FP and BPFN produce highly toxic effects on fish when given in combination or singly. To our knowledge, this is the first report on toxicity caused by FP and BPFN in single and combined state.

Molecular analysis of ATP-sensitive K+ channel subunits expressed in mouse portal vein

BackgroundSeveral combinations of inwardly rectifying K+ channel 6.x family pore-forming (KIR6.x) subunits associated with sulphonylurea receptor (SUR.x) subunits have been detected among ATP-sensitive K+ (KATP) channels. It remains to be established which of these is expressed in native vascular smooth muscle. MethodsPharmacological and electrophysiological properties of KATP channels in mouse portal vein were investigated using tension measurements and patch-clamp techniques. Molecular biological analyses were also performed to investigate the structural properties of these channels. ResultsSpontaneous contractions in mouse portal vein were reversibly reduced by pinacidil and MCC-134, and the pinacidil-induced relaxation was antagonized by glibenclamide and U-37883A. In cell-attached mode, pinacidil activated glibenclamide-sensitive K+ channels with a conductance (35 pS) similar to that of KIR6.1. RT-PCR analysis revealed the expression of KIR6.1, KIR6.2 and SUR2B transcripts. Using real-time PCR methods, the quantitative expression of KIR6.1 was much greater than that of KIR6.2. Immunohistochemical studies indicated the presence of KIR6.1 and SUR2B proteins in the smooth muscle layers of mouse portal vein and in single smooth muscle cells dispersed from mouse portal vein. ConclusionsThe results indicate that native KATP channels in mouse portal vein are likely to be composed of a heterocomplex of KIR6.1 and SUR2B subunits.

Design, characterization, and first-in-human study of the vascular actions of a novel biased apelin receptor agonist.

[Pyr(1)]apelin-13 is an endogenous vasodilator and inotrope but is downregulated in pulmonary hypertension and heart failure, making the apelin receptor an attractive therapeutic target. Agonists acting at the same G-protein-coupled receptor can be engineered to stabilize different conformational states and function as biased ligands, selectively stimulating either G-protein or β-arrestin pathways. We used molecular dynamics simulations of apelin/receptor interactions to design cyclic analogues and identified MM07 as a biased agonist. In β-arrestin and internalization assays (G-protein-independent), MM07 was 2 orders of magnitude less potent than [Pyr(1)]apelin-13. In a G-protein-dependent saphenous vein contraction assay, both peptides had comparable potency (pD2:[Pyr(1)]apelin-13 9.93±0.24; MM07 9.54±0.42) and maximum responses with a resulting bias for MM07 of ≈350- to 1300-fold for the G-protein pathway. In rats, systemic infusions of MM07 (10-100nmol) caused a dose-dependent increase in cardiac output that was significantly greater than the response to [Pyr(1)]apelin-13. Similarly, in human volunteers, MM07 produced a significant dose-dependent increase in forearm blood flow with a maximum dilatation double that is seen with [Pyr(1)]apelin-13. Additionally, repeated doses of MM07 produced reproducible increases in forearm blood flow. These responses are consistent with a more efficacious action of the biased agonist. In human hand vein, both peptides reversed an established norepinephrine constrictor response and significantly increased venous flow. Our results suggest that MM07 acting as a biased agonist at the apelin receptor can preferentially stimulate the G-protein pathway, which could translate to improved efficacy in the clinic by selectively stimulating vasodilatation and inotropic actions but avoiding activating detrimental β-arrestin-dependent pathways.

Role of Na+-K+-2Cl- Cotransporter 1 in Phenylephrine-Induced Rhythmic Contraction in the Mouse Aorta: Regulation of Na+-K+-2Cl- Cotransporter 1 by Ca2+ Sparks and KCa Channels

Background/Aims: Vasoconstrictor-induced rhythmic contraction of arteries or veins has been observed both in vivo and in vitro. Many studies have reported that gap junctions, ryanodine receptors, Na⁺, K⁺-ATPase and other factors are involved in vasoconstrictor-induced rhythmic contraction in vascular smooth muscle. However, the mechanism is still not completely understood. Methods: We used vessel tension measurements, intracellular recordings and intracellular Cl^- concentration ([Cl^-]_i) measurements to investigate the mechanism underlying phenylephrine (PE)-induced rhythmic contraction in the mouse aorta. Results: We found that Na⁺-K⁺-2Cl^- cotransporter 1 (NKCC1) inhibitor bumetanide abolished PE-induced rhythmic contraction. The Cl^- channel blockers DIDS and niflumic acid initially augmented the amplitude of PE-induced rhythmic contraction but later inhibited the rhythmic contraction. The large Ca²⁺-activated K⁺ channel blocker TEA and iberiotoxin increased the amplitude of PE-induced rhythmic contraction. The voltage-dependent Ca²⁺ channel blocker, nifedipine, and a Ca²⁺-free solution abolished PE-induced rhythmic contraction. The inhibitor of ryanodine receptors in the sarcoplasmic reticulum, ryanodine, inhibited PE-induced rhythmic contraction. Moreover, bumetanide hyperpolarized the membrane potential of vascular smooth muscle cells in a resting state or after PE pre-treatment. Bumetanide, niflumic acid, ryanodine, iberiotoxin, nifedipine and Ca²⁺-free buffer significantly suppressed the PE-induced [Cl^-]_i increase. Conclusion: These data indicate that NKCC1 is involved in the formation of PE-induced rhythmic contraction, and we also provide a method with which to indirectly observe the NKCC1 activity in isolated intact mouse thoracic aortas.

Bending and twisting the embryonic heart: a computational model for c-looping based on realistic geometry.

The morphogenetic process of cardiac looping transforms the straight heart tube into a curved tube that resembles the shape of the future four-chambered heart. Although great progress has been made in identifying the molecular and genetic factors involved in looping, the physical mechanisms that drive this process have remained poorly understood. Recent work, however, has shed new light on this complicated problem. After briefly reviewing the current state of knowledge, we propose a relatively comprehensive hypothesis for the mechanics of the first phase of looping, termed c-looping, as the straight heart tube deforms into a c-shaped tube. According to this hypothesis, differential hypertrophic growth in the myocardium supplies the main forces that cause the heart tube to bend ventrally, while regional growth and cytoskeletal contraction in the omphalomesenteric veins (primitive atria) and compressive loads exerted by the splanchnopleuric membrane drive rightward torsion. A computational model based on realistic embryonic heart geometry is used to test the physical plausibility of this hypothesis. The behavior of the model is in reasonable agreement with available experimental data from control and perturbed embryos, offering support for our hypothesis. The results also suggest, however, that several other mechanisms contribute secondarily to normal looping, and we speculate that these mechanisms play backup roles when looping is perturbed. Finally, some outstanding questions are discussed for future study.

Purinergic receptor stimulation induces Ca2+ oscillations and smooth muscle contraction in small pulmonary veins (1175.6)

The small intrapulmonary veins (SPV) are thought to participate in the control of pulmonary blood flow and its excessive contraction has been associated with the development of pulmonary edema. However, the regulation of smooth muscle contraction by intracellular signaling in SPV is poorly understood. We used rat lung slices with phase‐contrast and confocal microscopy to investigate Ca2+ signaling and contraction during purinergic receptor activation in small (100‐250 µm) pulmonary veins. We found that ATP induced strong, concentration‐dependent, and reversible vein contraction. Vein contraction was accompanied by intracellular Ca2+ oscillations that propagated along the vein smooth muscle cell as Ca2+ waves. In the absence of extracellular Ca2+, ATP induced Ca2+ oscillations that were attenuated in time and transient vein contraction. The InsP3 receptor inhibitor 2‐APB inhibited the Ca2+ oscillations and contraction induced by ATP in absence of extracellular Ca2+. In contrast, Ca2+ oscillations and contraction were resistant to ryanodine. Vein contraction was inhibited by phospholipase Cβ inhibitor U73122 and by purinergic receptor antagonist suramin. These results suggest that ATP is a strong vasoconstrictor of SPV and that ATP activate purinergic P2Y receptors in vein smooth muscle to induce InsP3 receptor‐mediated Ca2+ oscillations and vein contraction.Grant Funding Source: American Heart Association

Physiological Contractility of Cardiomyocytes in the Wall of Mouse and Rat Azygos Vein

We recently demonstrated the abundant presence of cardiomyocytes in the wall of thoracic veins of adult mouse and rat (Kracklauer, Feng, Jiang, Lin, Lin, Jin, FEBS J. 280:880-91, 2013). The highly differentiated morphology and myofilament protein expression of the venous cardiomyocytes suggested contractile functions. Here we further investigated the contractility of mouse and rat azygos venous rings in comparison with that of atrial strips and ventricular papillary muscle. X-gal staining of transgenic mouse vessels expressing lacZ under cloned cardiac troponin T promoter demonstrated that the venous cardiomyocytes are discontinuous from atrial myocardium and longitudinally aligned in the wall of thoracic veins perpendicular to the vessel axis. Histology study showed striation patterns in the venous cardiomyocytes, which indicate encirclement orientation of myofibrils in the vessel wall. Mechanical studies found that mouse and rat azygos veins produce strong cardiac type twitch contractions when stimulated by electrical pacing in contrast to the weak and slow smooth muscle contractions induced using 90 mM KCl. The twitch contraction and relaxation of rodent azygos veins further exhibited cardiac type beta-adrenergic responses. Quantitative characterization showed that the contractions of venous cardiomyocytes are slightly slower than that of atrium muscle but significantly faster than that of ventricular papillary muscle. These novel findings indicate that the cardiomyocytes in rodent thoracic veins possess fully differentiated cardiac muscle phenotype despite their anatomical and functional separation from the heart.

Usage of Systemic Therapy in Panic Attack Case: A Case Presentation

This work is about a case in which someone applied for consultancy with a problem of panic attack and the systemic therapy techniques were used for treatment. The researcher had completed the systemic therapy training at the Wenha m Institute of Family Therapy. A.Y. The subject was a 34 year old housewife with work experience in the recent past, graduated from the high school and married for 12 years. She was suffering from panic attack for the last 4-5 years. She used to get attacks once in nearly every 10 days for 3-4 days each time and these affected her quite badly. During the panic attacks she felt sick and threw up, beside the other feelings like palpitation, pain in groin, contraction in veins and exhaustion with shaking. These dramatic physical symptoms used to be accompanied by over anxiety. The subject who consulted for her panic attacks was using medicine for 5 years. A 10-seance systemic therapy model was applied to the subject at the Psychological Counseling Unit of Mersin University as one seance per week (1 or 1 ½ hrs each). 3 months after the completion of Systemic Therapy the observation phase was started. The subject admitted that she was back to work and both the frequency as well as the intensity of attacks decreased, with her own words she was now able to “dance” with it. The systemic therapy techniques applied to this subject were genogram, classification, analysis of power sources, party of pieces and ranging. Loop questions were used to help her in restructuri ng the problem and in finding new solutions by the help of new viewpoints and increase in her awareness. All in all, this case is noticeable as a promising therapy technique while working with subjects suffering from panic attack.

Endothelium dependent expression and underlying mechanisms of des-Arg9-bradykinin-induced B1R-mediated vasoconstriction in rat portal vein

Endothelial dysfunction has been implicated in portal vein obstruction, a condition responsible for major complications in chronic portal hypertension. Increased vascular tone due to disruption of endothelial function has been associated with an imbalance in the equilibrium between endothelium-derived relaxing and contracting factors. Herein, we assessed underlying mechanisms by which expression of bradykinin B1 receptor (B1R) is induced in the endothelium and how its stimulation triggers vasoconstriction in the rat portal vein. Prolonged in vitro incubation of portal vein resulted in time- and endothelium-dependent expression of B1R and cyclooxygenase-2 (COX-2). Inhibition of protein kinase C (PKC) or phosphatidylinositol 3-kinase (PI3K) significantly reduced expression of B1R through the regulation of transcription factors, activator protein-1 (AP-1) and cAMP response element-binding protein (CREB). Moreover, pharmacological studies showed that B1R-mediated portal vein contraction was reduced by COX-2, but not COX-1, inhibitors. Notably, activation of endothelial B1R increased phospholipase A2/COX-2-derived thromboxane A2 (TXA2) levels, which in turn mediated portal vein contraction through binding to TXA2 receptors expressed in vascular smooth muscle cells. These results provide novel molecular mechanisms involved in the regulation of B1R expression and identify a critical role for the endothelial B1R in the modulation of portal vein vascular tone. Our study suggests a potential role for B1R antagonists as therapeutic tools for diseases where portal hypertension may be involved.

Contractile effect of Sclerocarya birrea (A Rich) Hochst (Anacardiaceae) (Marula) leaf aqueous extract on rat and rabbit isolated vascular smooth muscles

Sclerocarya birrea (Anacardiaceae) is traditionally used for treating hypertension. The pharmacological effects of S birrea leaf aqueous extract (SBE) on rabbit and rat vascular smooth muscles were investigated in this study. Fresh S birrea leaves (1 kg) were air dried at 26 ± 1°C, milled, macerated in 2.5 l of distilled water for 48 hours, filtered, and the filtrate was concentrated in a rotary evaporator. Rat isolated portal vein preparations, as well as rabbit isolated endothelium-denuded and endothelium-intact descending thoracic aortic ring preparations were mounted in 30-ml Ugo Basile organ baths under physiological conditions, and challenged with SBE (50-400 mg/ml). The contractile effects of SBE and/or other reference drugs on the isolated vascular smooth muscle preparations were recorded by means of Ugo Basile's force-displacement transducers and Gemini recorders. SBE (50-400 mg/ml) caused a significant, concentration-dependent upward shift in baseline tone in the aortic ring preparations (p < 0.01-0.001). Indomethacin (20 µM) markedly attenuated the contractile effects of SBE in both the endothelium-intact and -denuded aortic rings, while N(G)-nitro-(L)-arginine methyl ester (L-NAME, 100 µM) significantly (p < 0.05) increased the contractile tension of the endothelium-intact aortic rings. Verapamil (1-3 µg/ml) partially inhibited the contractile effects of SBE. SBE also elicited significant (p < 0.05-0.01) increases in the amplitude of the myogenic contractions of the portal veins. These contractions were abolished by verapamil (1-3 µg/ml) in a concentration-dependent manner, while prazosin (1-3 µg/ml) did not affect the SBE-induced contractions. SBE possessed spasmogenic effects on vascular smooth muscle preparations in vitro. It may induce and/or exacerbate hypertension, contrary to the folkloric, ethnomedical use of S birrea.

Effects of oxygenation and luminal flow on human placenta chorionic plate blood vessel function

The human fetoplacental vasculature has been suggested to be a low resistance/high flow system, but the mechanisms by which this state is achieved are unclear. This study assessed the effects of intraluminal flow and local oxygenation on isolated human placental chorionic plate arteries and veins at term using pressure myography. Chorionic plate arteries and veins exhibit myogenic tone. A small but significant arterial vasodilatation was observed following exposure to hypoxia; chorionic plate veins contracted to a similar hypoxic stimulus. Under physiological conditions of pressure and oxygenation, increased luminal flow induced contraction in both chorionic plate arteries and veins. [Correction added after online publication 15th November 2011: 'induced vasodilatation' has been changed to 'induced contraction'] Human fetoplacental vascular tone can be manipulated by local physical factors.

Characteristics of the actions by which 5‐HT affects electrical and mechanical activities in rabbit jugular vein

5-HT is known to be a potent vasospasmogenic agonist in various arteries. However, in veins the vasomodulating actions of 5-HT, and the underlying mechanisms, remain to be fully clarified. Here, we characterized the actions by which 5-HT affects electrical and mechanical activities in the rabbit jugular vein. Membrane potential and isometric tension were measured in endothelium-intact and -denuded preparations. Localization of 5-HT receptor subtypes was examined immunohistochemically. 5-HT induced a transient then a small, sustained smooth muscle cell hyperpolarization in endothelium-intact strips. In endothelium-denuded strips, 5-HT induced only a sustained hyperpolarization, and this was changed to a depolarization by the selective 5-HT(7) receptor inhibitor SB269970. This depolarization was inhibited by the 5-HT(2A) receptor blocker sarpogrelate. 5-HT induced a relaxation of PGF(2α) -induced contracted strips that was similar in endothelium-intact and -denuded preparations. The latter relaxation was changed to contraction by SB269970 and this contraction was inhibited by sarpogrelate. Immunoreactive responses against endothelial and smooth muscle 5-HT(2A) receptors and smooth muscle 5-HT(7) receptors were identified in the vein. The 5-HT-induced relaxation of the PGF(2α) contraction was inhibited by the cAMP-dependent protein kinase inhibitor Rp-cAMPS and by the AC inhibitor SQ22536. These results indicate that 5-HT activates both smooth muscle 5-HT(7) receptors (to produce relaxation) and smooth muscle 5-HT(2A) receptors (to produce contraction) in rabbit jugular vein. We suggest that in this particular vein, the 5-HT(2A) receptor-induced depolarization and contraction are masked by the 5-HT(7) receptor-induced responses, possibly via actions mediated by cAMP.

Ca 2+−dependent contraction by the saponoside escin in rat vena cava: Implications in venotonic treatment of varicose veins

Saponosides (horse chestnut seed extract, escin) and flavonoids (diosmin, Daflon 500, Servier, France) exhibit venotonic properties that have been utilized in treatment of varicose veins. However, the cellular mechanisms underlying the venotonic properties of escin and diosmin are unclear. Because Ca(2+) is a major regulator of venous smooth muscle (VSM) function, we tested the hypothesis that escin and diosmin promote Ca(2+)-dependent venous contraction. Rings of inferior vena cava (IVC) from male rats were suspended in a tissue bath for measurement of isometric contraction. Following control contraction to 96 mM KCl, the effects of escin and diosmin (10(-10) to 10(-4) M) on vein contraction were measured. To test the role of intracellular Ca(2+) release, the vein response to escin and diosmin was measured in Ca(2+)-free (2mM EGTA) Krebs. To test for Ca(2+)-dependent effects, IVC segments were pretreated with escin or diosmin (10(-4) M) in 0 Ca(2+) Krebs, then extracellular CaCl(2) (0.1, 0.3, 0.6, 1, 2.5 mM) was added and the [Ca(2+)](e)-contraction relationship was constructed. To test for synergistic effects of diosmin, IVC segments were pretreated with diosmin (10(-4) M), then stimulated with KCl (16-96 mM) or escin (10(-10) to 10(-4) M) and vein contraction was measured. Contraction data were presented as mg/mg tissue (means ± SEM). In IVC segments incubated in normal Krebs (2.5 mM Ca(2+)), escin caused concentration-dependent contraction (max 104.3 ± 19.6 at 10(-4) M). Escin-induced contraction was not a rigor state, because after washing with Krebs, the veins returned to a relaxed state. In Ca(2+)-free Krebs, there was essentially no contraction to escin. In escin-treated veins incubated in 0 Ca(2+) Krebs, stepwise addition of extracellular CaCl(2) caused corresponding increases in contraction (max 80.0 ± 11.1 at 2.5 mM). In the absence of escin, the α-adrenergic agonist phenylephrine (PHE, 10(-5) M), angiotensin II (AngII, 10(-6) M), and membrane depolarization by KCl (96 mM) caused significant contraction (122.5 ± 45.1, 114.2 ± 12.2 and 221.7 ± 35.4, respectively). In IVC segments pretreated with escin (10(-4) M), the contractile response to PHE (9.7 ± 2.6), AngII (36.0 ± 9.1), and KCl (82.3 ± 10.2) was significantly reduced. Diosmin (10(-4) M) caused small contractions in normal Krebs (11.7 ± 1.9) and Ca(2+)-free Krebs (4.2 ± 2.2). In diosmin-treated veins incubated in 0 Ca(2+) Krebs, addition of extracellular CaCl(2) caused minimal contraction. Diosmin did not enhance the IVC contraction to PHE, AngII, or escin, but enhanced the contractile response to KCl (24-51 mM). In rat IVC, escin induces extracellular Ca(2+)-dependent contraction, but disrupts α-adrenergic and AT(1)R receptor-mediated pathways and depolarization-induced contraction. The initial venotonic benefits of escin may be offset by disruption of vein response to endogenous venoconstrictors, limiting its long-term therapeutic benefits in varicose veins. Diosmin does not cause venous contraction or potentiate the venotonic effects of endogenous venoconstrictors or escin ex vivo, and its use as venotonic may need to be further evaluated.

Endothelin‐1 increases the frequency of smooth muscle calcium waves in vena cava but not aorta

Vascular contraction is associated with a global increase in smooth muscle Ca2+. The frequency and amplitude of localized intracellular Ca2+ release events, such as IP3 receptor‐mediated Ca2+ waves, can also regulate excitation‐contraction coupling in smooth muscle. While the vasoconstrictor ET‐1 does increase IP3 formation, it is unclear if IP3 receptor‐mediated Ca2+ waves are a regulator of ET‐1‐induced contraction in arteries and veins. We hypothesized that ET‐1 increases the frequency and amplitude of Ca2+ waves in rat aorta (RA) and vena cava (RVC). RA and RVC were mounted en face in an imaging superfusion chamber and incubated with the intensiometric fluorescent Ca2+ indicator Fluo 4‐AM (10 μM). Using spinning‐disc confocal microscopy, image sequences were first recorded with buffer alone, and then maximal contractile concentrations of norepinephrine (NE, 10 μM) (RVC) or phenylephrine (PE, 10 μM) (RA), and finally ET‐1 (100 nM). ET‐1 (100 nM) increased Ca2+ wave frequency significantly in RVC versus control (0.72±0.16 Hz vs. 0.45±0.13 Hz), but not in RA. Neither NE (10 μM) nor PE (10 μM) altered Ca2+ wave frequency or amplitude in RA and RVC. These data indicate that intracellular Ca2+ mobilization by ET‐1 is different in arteries and veins. These data also provide indirect evidence that ET receptors are coupled to IP3‐mediated Ca2+ release mechanisms in the vena cava but not aorta. Supported by NIH P01HL70687.

M1 and M3 Muscarinic Receptors Mediate Relaxation and Contraction in Canine Nasal Veins

Acetylcholine (ACh) has been shown to induce nasal congestion via vasorelaxation of intranasal posterior collecting veins (PCV) coupled with vasocontraction of extranasal outflow veins (dorsal nasal vein [DNV] and sphenopalatine vein [SPV]). The aim of this study was to characterize the muscarinic receptor subtype(s) involved in ACh-induced relaxation and contraction in canine nasal veins. PCV, DNV, and SPV were isolated from the canine nose. In vitro isometric tension of segments from these veins was monitored to reflect vascular reactivity. ACh concentration-response curve was studied in the presence of muscarinic receptor subtype inhibitors. Immunohistochemical localization of M(1)-M(5) receptor subtypes in the veins was performed. ACh-induced relaxation in PVC was inhibited by pertussis toxin (PTX; inhibitor of G-protein that couples M(2)/M(4) receptors), methoctramine (selective M(2) muscarinic receptor inhibitor), muscarinic toxin 7 (MT-7; selective M(1) muscarinic receptor inhibitor), and 4-diphenylacetoxy-methylpiperidine methiodide (4-DAMP; selective M(3) muscarinic receptor inhibitor). ACh-induced contraction in SPV and DNV was potentiated by PTX and methoctramine but was inhibited by MT-7 and 4-DAMP. Immunohistochemistry confirmed the presence of five muscarinic receptor subtypes in the endothelium of nasal veins, with staining of M(3) > M(1) > M(5) > M(2) = M(4) in PVC but M(2) = M(4) > M(3) > M(1) > M(5) in outflow veins. M(1) and M(3) receptor subtypes were localized in the smooth muscles of both types of veins. The results show that ACh relaxes intranasal veins and contracts extranasal veins primarily via M(1) and M(3) muscarinic receptor subtypes, implying the therapeutic value of M(1)/M(3)-specific or highly selective anticholinergics on nasal congestion.